Various PFC are conventionally used as dry etching gases. However, since PFC are very stable in the atmosphere and high in global warming coefficient, emission of PFC is required to be reduced in amount. Recently, fluoroether compounds attract attention as dry etching gases. Among fluoroether compounds, fluorine-containing oxetanes are considered advantageously usable as dry etching gases since they easily decompose in the atmosphere because of their chemically unstable four-member ring structure.
A process for synthesizing 2,2,3,3,4,4-hexafluorooxetane, one of the fluorine-containing oxetanes, is disclosed in German Patent No. 814002. The process comprises electrolytically fluorinating an oxetane in hydrogen fluoride. The process, however, is not satisfactory since the oxetane easily decomposes during the reaction, producing a large amount of by-products.
A number of researches have been made on hydrogen-fluorine substitution reaction of organic compounds using fluorine gas (e.g., Lagow et al., J. Org. Chem., 42, 3437 (1977)). However, known processes require special reactors since fluorine is highly reactive and may cause a runaway reaction or explosion. Further, they require a low reaction temperature of -78.degree. C. and a large amount of diluent gas in order to prevent side reactions such as cleavage of the carbon-carbon bond of the organic compound. Thus, known processes are not satisfactory for industrial purposes.